This disclosure relates to infrared transmissive thermoplastic compositions, articles formed therefrom, and uses thereof.
The increased variety of small, portable electronic devices has led to a commensurately increased need to adapt the aesthetic form of such devices to the desired functions they provide. For devices such as calculators, television remote controls, multi-functional cellular telephones, personal digital assistants (PDA's), laptop computers, wireless mouses, computer keyboards, and other similar items, signal and/or data information transfer between the device and a complementary device (such as between an optical mouse and computer) is generally accomplished by using either a radio frequency broadcast signal between the devices, or more commonly line-of-sight infrared signal transmitted between the devices. The latter is useful for short-range inter-device communication.
Devices that communicate via transmitted infrared signals require both a transmission source and/or a receiver in each device. Since typical materials of construction of the cases for such devices have a variety of fillers, additives, and are formed from a variety of different thermoplastics, the transmissivity of the cases is not typically high enough to permit the placement of the infrared source and receiver within the case. Optical windows that are transparent in the infrared are frequently used to provide an optical pathway into and out of the casing in such devices. Typically, the optical windows are formed from an infrared-transparent plastic material with low light scattering properties, and may be clear or opaque. It is desirable for these windows absorb visible light (i.e., to be opaque to the eye), to filter out the effects of stray light. However, to provide the desired absorbance, the windows are generally dark in color (red to black), which can give the device an appearance that may not be aesthetically appealing, and which can have limited decorative capability.
There accordingly remains a need in the art for thermoplastic compositions for use in infrared transmissive windows or other infrared transmissive applications, which have improved appearance while maintaining the desired light transmissive properties for infrared and visible light.